Mosquito-borne diseases, such as malaria, filariasis, and dengue, remain significant pathogens of humans and animals and are intractable to control or are resurgent in many areas of the world. Conventional mechanisms have proven to be ineffectual in controlling these diseases. Application of modern molecular tools and approaches should remove the "black box' view of the vector in terms of vectobiology, vector-pathogen interactions, vector competence, and other components of vector-pathogen amplification and maintenance cycles in nature. The long term goal of this research is to exploit such new information concerning vector biology or vector-pathogen interactions to develop novel control strategies for vector-borne diseases, which target the invertebrate vector. In this project, we will exploit viruses that naturally-infect mosquitoes to investigate the molecular biology of vectors and vector-pathogen interactions. Genes and gene produced identified as determinants of malaria and filaria transmission in other projects of this TDRU proposal will be characterized in vitro and in vivo using virus delivery and expression systems. Two viruses will be utilized; Sindbis an Aedes densonucleosis (AeDNV). The SIN virus (Togaviridae) system will be used to stably, "cytoplasmically transform" mosquito cells and to express or knock out genes, which are potentially determinants of vector-pathogen interactions. Similarly, genes identified as potential targets for development of transgenic, parasite-resistant organisms (or other genes necessitating DNA-based expression systems) will be characterized using the AeDNV (Parvoviridae) expression system. These two virus expression systems provide extremely powerful additions to the armentarium of vector molecular biologists and much useful information concerning the molecular biology of parasite vectors will undoubtedly be forthcoming. These proposed studies will also provide considerable information about the feasibility of developing a new generation of biocontrol agents from control of vectors. The AeDNV expression system provides unique biocontrol potential. aroviruses are extremely resistant to environmental degradation, and naturally infect a wide range of vector species. The AeDNV expression system will be used to transduce genes into mosquito larvae that repress host seeking behavior, are mosquitocidal, make vectors incompetent, or inhibit vector host development. Both the AeDNV and the gene products involved (eg -Aedes head peptide, juvenile hormone esterase) are species specific, which is most desirable for biocontrol agents.